I have not been to the Galapagos, so I can't provide advice re: the experience. But, it is on my list of places I hope to visit.
But, since you have asked some questions about meds to prevent seasickness, I will share some info that I never knew before our recent trip (which was a National Geographic Expedition to Iceland and Greenland). I had NEVER had any problem with seasickness before (10 different ship journeys), including experiencing over 45-foot waves at the tip of New Zealand during gale-force winds and also during medium waves (10-20 feet) both ways through Drake's Passage en route to/fro Antarctica. So, you can imagine my surprise when I began I suddenly began to feel light-headed at the beginning of dinner off the coast of Greenland when there was just a bit of ocean motion, but not that much motion compared to other times when I was never bothered. I excused myself from dinner and knew to lay flat in bed (took care of the problem without any other drama).
When I mentioned how odd it was to the ship's hotel manager the next day, he asked me if I had consumed any citrus ( I had two mimosas before dinner), and he explained that citrus can make one more susceptible to seasickness symptoms. I found that VERY interesting, and I avoided citrus in the evening for the rest of the journey and had no further issues. So, you might want to mentally file that away, just in case you have issues that may cause you to choose to avoid citrus. Spicy and greasy food, I have since been told, can also contribute.
I seem do better overall without the seasickness tablets (which bother my stomach when the waves did not).
And, I've also been told that other than laying flat, it is a good idea (if you are up top side) to keep an eye on the horizon if you begin to be bothered by wave motion. If the seas are exceptionally rough at night, I keep the blinds/drapes closed and NEVER look out the cabin window, as I think that might cause anxiety for me to see rough waves knocking against the window...hearing it is enough ;o
Wishing you a very special experience and calm seas.